JP2017170552A - Position control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the position of a robot without performing correction on the basis of absolute position accuracy.SOLUTION: A control device 13 of a position control system 11 is configured to transmit a stop command for instructing a stop position of an end effector 2 to a robot 1. The control device 13 includes: a position accuracy calculation unit 23a which calculates a deviation between a command position related to the stop command and an achieving position of the end effector 2 measured by a measuring device 12; and a determination unit 23b which determines whether the deviation is in the range of a prescribed reference value. The control device 13 is configured to repeatedly transmit the stop command related to the stop position to the robot 1 until the determination unit determines that the deviation is in the range of the prescribed reference value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a position control system capable of controlling a stop position of a robot with high accuracy.

  In recent years, automation by various robots has been promoted in order to improve productivity in factories and the like. As this robot, for example, a multi-degree-of-freedom arm equipped with a multi-joint arm is widely used, and various end effectors are detachably attached to the tip of the robot so that it can handle various work. Yes.

  This robot may be in a position / posture different from the required position / posture due to the effects of the length of the arm, the weight of the end effector, the deflection of the robot, and the accuracy thereof may be deteriorated. In order to maintain high accuracy regarding the position and posture of the robot, it is necessary to perform calibration (calibration) every time the robot state changes or periodically.

  In general, a technique for obtaining the accuracy of the absolute position of the end effector of the robot is called robot arm calibration. As a technique relating to calibration, Patent Document 1 discloses that these three laser displacement sensors and an arrangement that can simultaneously measure the distances to three planes of an object that are non-parallel to each other and whose angles formed with each other are known. A robotic measurement sensor device having means for supporting a laser displacement sensor of a table is disclosed.

  Further, in this Patent Document 1, this measurement sensor device is mounted on a vertical articulated robot, and the angles of the objects that are non-parallel to each other using the measurement sensor device at a plurality of different robot positions are known. A calibration method is disclosed in which a distance to a certain three planes is measured, and the position and orientation of the object viewed from the sensor coordinate system are determined based on the measurement data and data representing a known angular relationship between the three planes of the object. Yes.

JP-A-7-121214

  The conventional calibration method accurately determines the absolute position accuracy of the robot. However, when this method is applied to, for example, a vertical articulated robot, the structure is as small as several tens of μm to several mm. Correction is difficult.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a position control system capable of executing a suitable position adjustment of a robot without considering absolute position accuracy.

  The present invention is to solve the above-described problem, and in a position control system that performs position control of a robot having an end effector, a measuring device that measures a stop position of the end effector, the measuring device, and the A control device for controlling the robot, wherein the control device is configured to transmit a stop command for instructing the stop position of the end effector to the robot, and the control device includes a command related to the stop command. A position accuracy calculation unit that calculates a deviation between the position and the realized position of the end effector measured by the measurement device; a determination unit that determines whether the deviation is within a predetermined reference value range; The control device includes the stop instruction to the robot until the determination unit determines that the deviation is within a predetermined reference value range. Characterized in that it is configured to repeatedly transmit the.

  According to such a configuration, the deviation between the command position of the end effector and the actual position is calculated by the position accuracy calculation unit of the control device, and the position adjustment of the end effector can be suitably executed by determining the deviation by the determination unit. . That is, the control device completes the position adjustment when the deviation between the command position and the actual position is within a predetermined reference value range, but when the deviation is outside the reference value range, In order to continue this position adjustment, a stop command is continuously transmitted to the robot. Thereby, the position adjustment can be reliably executed without performing correction based on the absolute position accuracy of the end effector.

  According to the present invention, it is possible to adjust the position of the robot without performing correction based on absolute position accuracy.

It is a conceptual diagram of a position control system. It is a functional block diagram of a position control system. It is a conceptual diagram which shows a part of operation | movement in a position control system. The example of the image data acquired by an imaging device is shown. The example of the image data acquired by an imaging device is shown.

  Hereinafter, embodiments for implementing a position control system according to the present invention will be described with reference to the drawings.

  1 to 5 show an embodiment of a position control system according to the present invention. For example, a vertical articulated robot is used as a target of position control (position adjustment). As shown in FIG. 1, the robot 1 is coupled to a coupling device 3 that can connect (couple) an end effector 2, a first joint 4 coupled to the coupling device 3, and the first joint 4. A first arm 5, a second arm 6 that supports the first arm 5, a second joint 7 that connects the first arm 5 and the second arm 6, and a base 8 that supports the second arm 6, A third joint 9 that connects the second arm 6 and the base 8 is provided.

  The robot 1 according to the present embodiment operates the end effector 3 three-dimensionally by 6-axis control using the first joint 4, the second joint 7, and the third joint 9, but is not limited thereto. Other than those, other multi-axis multi-joints (for example, 7-axis control) can be used. The robot 1 according to this example includes one axis of rotation on the base 8, one axis of oscillation of the second arm 6 by the third joint 9, one axis of oscillation of the first arm 5 by the second joint 7, The end effector 2 is operated by one axis of rotation of one arm 5, one axis of swinging of the end effector 2 by the first joint 4, and one axis of rotation of the end effector 2 at the tip.

  In the present embodiment, when the two steel plates WA and WB (workpieces) are welded as the end effector 2 attached to the coupling device 3 of the robot 1, a positioning pin that performs positioning of these steel plates is exemplified (hereinafter, referred to as “positioning pins”). The common code 2 is used for the end effector and the positioning pin). As shown in FIG. 1, the two steel plates WA and WB are formed with through holes 10a and 10b for positioning, and the positioning pin 2 is inserted into the through holes 10a and 10b. These positioning is performed.

  As shown in FIG. 1, the position control system 11 includes a measuring device 12 that measures the position of the end effector 2 in the robot 1, and a control device 13 that controls the measuring device 12 and the robot 1.

  The measuring device 12 includes a projection device 15 that projects an image 14 having a predetermined shape, a screen 16 on which the image 14 is projected, and an imaging device 17 that captures the image 14 projected on the screen 16. The measurement device 12 is not limited to this configuration, and may be configured to measure the position of the end effector 2 by, for example, one or a plurality of gyro sensors attached to the end effector 2 and the robot 1.

  As shown in FIG. 1, the projection device 15 is fixed at an arbitrary position of the robot 1, but is preferably provided as close to the end effector 2 as possible. From this point of view, the projection device 15 is attached to the tip of the robot 1, that is, the coupling device 3. Further, the projection device 15 may be provided directly on the end effector 2. The projection device 15 includes a light source (not shown) and a slit 18 (see FIG. 2) provided close to the light source.

  In the present embodiment, a laser light source capable of emitting diffused laser light is employed as the light source, but the present invention is not limited to this, and various other light sources such as an LED light source can be used. In the present embodiment, the slit 18 is configured in a cross shape, and the diffused laser light that has passed through the slit 18 is projected on the screen 16 as a cross-shaped image 14. The cross-shaped image 14 is for specifying the position of the end effector 2. For this purpose, it is desirable to grasp the positional relationship (for example, distance) between the projection device 15 and the end effector 2 in advance, and it is desirable that the data is recorded in the control device 13.

  For the screen 16, for example, a roll screen type or a plate that can be folded and the like can be easily transported. In addition, the screen 16 may be configured to be suspended on a ceiling of a factory or the like and to be lowered during use. The screen 16 is installed at a predetermined distance from the robot 1 when the position adjustment of the robot 1 is executed.

  The screen 16 has a projection surface 16a on which the image 14 by the projection device 15 is projected. The projection surface 16a is installed so as to be parallel to a surface along the yz direction in the coordinate system (orthogonal coordinate system) of the robot 1 set in the present embodiment.

  As the imaging device 17, various imaging cameras such as a CCD camera are used. The imaging device 17 is provided at a position where the entire screen 16 can be imaged. The image pickup device 17 can pick up the image 14 projected from the projection device 15 by picking up an image of the screen 16 and store it as image data. Further, the imaging device 17 can transmit this image data to the control device 13.

  The control device 13 is configured by a personal computer, for example, and is mounted with various hardware such as a CPU, RAM, ROM, HDD, driver, display, and input / output interface. Further, the control device 13 may be integrated into an NC control device that controls the operation of the robot 1.

  As illustrated in FIG. 2, the control device 13 includes a robot control unit 19 that controls the robot 1, a projection device control unit 20 that controls the projection device 15, an imaging device control unit 21 that controls the imaging device 17, and various types. A storage unit (RAM, ROM, HDD, etc.) 22 for storing the programs and data, and an arithmetic unit (CPU, etc.) 23 for performing various calculations. These components 18 to 22 are connected to each other by a bus (not shown).

  The robot control unit 19 is connected to the robot 1 and controls the joints 4, 7, and 9 of the robot 1 according to a signal (command) transmitted from the calculation unit 23, and executes a positioning operation using the positioning pins 2. . The projection device control unit 20 performs on / off control of the light source in the projection device 15 by a signal (command) transmitted from the calculation unit 23.

  The imaging device control unit 21 includes an image processing unit 21 a that is connected to the imaging device 17 and executes processing of image data acquired by the imaging device 17. The storage unit 22 is a control program for controlling the robot 1, the projection device 15, and the imaging device 17, a program for executing position adjustment of the robot 1, various data tables, image data acquired by the imaging device 17, and The identification data of the robot 1 is stored.

  The calculation unit 23 performs control on the robot 1 and the measurement device 12 by performing calculation processing on various programs and data stored in the storage unit 22. The calculation unit 23 transmits a signal for controlling the robot 1 and the measurement device 12 via the robot control unit 19, the projection device control unit 20, and the imaging device control unit 21.

  In addition, the calculation unit 23 is configured to execute a position adjustment program stored in the storage unit 22 and adjust the position of the robot 1. Specifically, the calculation unit 23 includes a position accuracy calculation unit 23a and a determination unit 23b.

  The position accuracy calculation unit 23a calculates a stop position related to a stop command for the end effector 2 (hereinafter referred to as “command position”) and a stop position of the end effector 2 measured by the measuring device 12 (hereinafter referred to as “realized position”). Calculate the deviation.

  The determination unit 23b determines whether the position accuracy (deviation) of the end effector 2 calculated by the position accuracy calculation unit 23a is within a predetermined reference value range. As the reference value, a value with higher accuracy than the repeat stop accuracy of the robot 1 is set. For example, in the case of the robot 1 having a repeat stop accuracy of ± 0.2 mm, the reference value can be set to ± 0.1 mm, but is not limited thereto. The repeat stop accuracy is calculated according to, for example, JIS B 8432 (pause accuracy, pause repeat accuracy).

  The calculation unit 23 continues or ends the position adjustment of the end effector 2 according to the determination result of the determination unit 23b. That is, when the determination unit 23b determines that the deviation is within the range of the reference value, the control device 13 stops the robot 1 on the assumption that the position adjustment of the robot 1 has been completed. When the determination unit 23b determines that the deviation is outside the range of the reference value, the control device 13 continues adjustment of the position of the robot 1 because the adjustment is insufficient.

  Hereinafter, the principle relating to the position adjustment of the robot 1 by the calculation unit 23 will be described in detail with reference to FIGS. 3 to 5.

  As shown in FIG. 3, the control device 13 controls the robot 1 to issue a stop command to the robot 1 in order to stop the end effector 2 at a predetermined position while operating the end effector 2 along the predetermined loop trajectory RO. Send.

  As the stop position, as shown by a two-dot chain line in FIG. 3, a position where the steel plates WA and WB can be actually positioned (hereinafter referred to as “inspection position”) and an inspection position as shown by a solid line And at least two locations in the vicinity immediately before (hereinafter referred to as “preparation position”). After temporarily stopping the end effector 2 at the preparation position, the control device 13 moves the end effector 2 in a predetermined direction and stops it at the inspection position. The control device 13 includes encoders included in the joints 4, 7, and 9 of the robot 1 so that the robot 1 takes a predetermined posture corresponding to the robot 1 to stop at the preparation position and the inspection position. Send a command to.

  4 and 5 show examples of image data acquired by the imaging device 17 when the end effector 2 stops at the inspection position. FIG. 4A shows image data obtained by imaging the image 14 </ b> A projected from the projection device 15 onto the screen 16 by the imaging device 17 when the end effector 2 is accurately arranged at the command position.

  As shown in FIG. 4A, the image 14A is configured in a cross shape having a vertical line 24A and a horizontal line 25A. Specifically, this image 14A is a regular cross in which the length LA1 of the vertical line 24A is equal to the length LA2 of the horizontal line 25A, the vertical line 24A is along the vertical direction, and the horizontal line 25A is oriented in the horizontal direction. Configured in shape.

  The image 14A serves as a reference when the position adjustment of the robot 1 is executed (hereinafter, this image is referred to as “reference image”). In the present embodiment, the image data including the reference image 14A is stored in the storage unit 22 of the control device 13 as reference image data. When the position adjustment of the robot 1 is executed, the image data for inspection acquired by the imaging device 17 and the reference image data (reference image 14A) are calculated by the calculation unit 23 (position accuracy calculation unit 23a) of the control device 13. ).

  FIGS. 4B to 4D and FIGS. 5A to 5C show examples of this comparison. When the position adjustment of the robot 1 is performed, the imaging device 17 acquires image data relating to an inspection image (hereinafter referred to as “inspection image”) 14 </ b> B projected on the screen 16. The image processing unit 21a of the imaging device control unit 21 in the control device 13 generates these combined image data by image processing so that the image data related to the inspection image 14B can be compared with the reference image 14A of the reference image data. To do. In this composite image data, as shown in FIG. 4B, the relationship between the reference image 14A and the inspection image 14B is shown (hereinafter the same in FIGS. 4C, 4D, and 5).

  FIG. 4B shows composite image data when the inspection image 14B is shifted in the y-axis direction (right side) in the coordinate system with respect to the reference image 14A. In this case, the inspection image 14B has the same shape (congruent) as the reference image 14A, and the coordinate position in the z-axis direction in the coordinate system of the robot 1 is the same as that of the reference image 14A.

  In this example, if the distance between the reference image 14A and the inspection image 14B is D1, the end effector 2 is at a position (realized position) that is separated from the command position by this distance D1 in the y-axis direction. . Therefore, if the distance D1 is known, the deviation between the command position of the end effector 2 and the actual position becomes clear.

  FIG. 4C shows an example of composite image data when the position (realized position) of the end effector 2 is shifted from the command position in the z-axis direction in the coordinate system. In this example, the inspection image 14B is at a position shifted from the reference image 14A along the z-axis of the coordinate system.

  In this case, it is assumed that the inspection image 14B has the same shape (congruent) as the reference image 14A, and the coordinate position in the y-axis direction in the coordinate system of the robot 1 is the same as that of the reference image 14A. In this example, if the inspection image 14B is separated from the reference image 14A by a distance D2 in the z-axis direction, the distance D2 is calculated by the position accuracy calculation unit 23a as a deviation between the command position of the end effector 2 and the actual position. Is done.

  FIG. 4D shows an example of composite image data when the realization position of the end effector 2 is deviated from the command position on the x axis in the coordinate system. In this example, the inspection image 14B has the same coordinate position in the z-axis direction and the y-axis direction in the coordinate system as the reference image 14A.

  However, the inspection image 14B is in an enlarged state than the reference image 14A. When the inspection image 14B is similar to the reference image 14A, the realized position of the end effector 2 is shifted away from the screen 16 relative to the command position in the x-axis direction. The position accuracy calculation unit 23a calculates the deviation between the command position of the end effector 2 and the actual position in the x-axis direction by comparing the reference image 14A and the inspection image 14B and obtaining the ratio thereof.

  As other examples, as shown in FIG. 5A, when the inspection image 14B is inclined (inclined at an angle θ with respect to the reference image 14A), or as shown in FIG. 5B. When the length LB1 of the vertical line 24B in the image 14B is shorter than the length LA1 of the vertical line 24A in the reference image 14A, the length LB2 of the horizontal line 25B in the inspection image 14B is as shown in FIG. The case where it becomes shorter than length LA2 of the horizontal line 25A in the reference | standard image 14A etc. is mentioned. Even in these cases, the position accuracy calculation unit 23a of the calculation unit 23 can calculate the deviation between the command position and the actual position in the end effector 2 by comparing the inspection image 14B with the reference image 14A.

  Hereinafter, a position control method (position adjustment method) of the robot 1 executed using the position control system 11 having the above configuration will be described.

  The target robot 1 is previously subjected to zero adjustment (origin adjustment) using a coordinate measuring machine. At this time, it is desirable to acquire the reference image data using the position control system 11. Specifically, the screen 16 and the imaging device 17 are arranged at predetermined positions, the inspection position of the end effector 2 is determined, and the image 14A is projected from the projection device 15 to the screen 16 with the end effector 2 stopped at the inspection position. Project.

  At this time, the reference image 14A projected on the projection surface 16a is picked up by the image pickup device 17 together with the screen 16, and thereby the reference image data is acquired. The reference image data (master data) is stored in the storage unit 22 of the control device 13 in a state in which data such as the shape of the reference image 14A and the coordinate position of the reference image 14A are associated with each other.

  For example, after the robot 1 has been used for a certain period, the position control system 11 adjusts the position of the robot 1. As shown in FIG. 3, the position control system 11 controls the robot 1 so that the end effector 2 is repeatedly moved along a predetermined loop trajectory RO.

  Specifically, the control device 13 transmits a control signal (stop command) to the robot 1 via the robot control unit 19 to temporarily stop the end effector 2 at the preparation position on the loop trajectory RO, and then at least one axis. For example, the end effector 2 is moved in the tool axis direction (the axial center direction of the positioning pin 2) and stopped at the inspection position. Note that the screen 16 and the imaging device 17 are installed at the same predetermined position as when the reference image data is acquired.

  When the end effector 2 stops at the inspection position, the control device 13 transmits a signal for projecting the inspection image 14 </ b> B to the projection device 15 via the projection device control unit 20. The projection device 15 turns on the light source according to this signal, and projects the inspection image 14B toward the screen 16.

  Further, the control device 13 transmits a signal for capturing the inspection image 14 </ b> B projected on the screen 16 to the imaging device 17 via the imaging device control unit 21. Upon receiving this signal, the imaging device 17 captures the inspection image 14B projected on the projection surface 16a of the screen 16, and transmits this image data to the image processing unit 21a. In the image processing unit 21a, a combining process of the reference image data and the acquired image data for inspection is executed. The composite image data thereby is transmitted from the imaging device control unit 21 of the control device 13 to the calculation unit 23.

  When the end effector 2 is at the same position as the command position, the reference image 14A and the inspection image 14B should be completely coincident with each other in the above synthesis process. However, when the actual position of the end effector 2 is different from the command position, the acquired inspection image 14B does not coincide with the reference image 14A, and the position, shape, size, and the like are synthesized in a state different from the reference image 14A. It appears in image data (see FIGS. 4B to 4D and FIGS. 5A to 5C).

  In this case, the control device 13 causes the position adjustment program stored in the storage unit 22 to be activated by the calculation unit 23, and causes the position accuracy calculation unit 23a to calculate the deviation between the command position and the realized position. Thereafter, the control device 13 causes the determination unit 23b to determine the calculated deviation. When it is determined that the deviation is outside the range of the reference value, the calculation unit 23 controls the robot 1 to move the end effector 2 on the loop trajectory RO, temporarily stop at the preparation position, and then inspect again. Move to position.

  Thereafter, as described above, acquisition of image data of the end effector 2 stopped at the inspection position, calculation of the deviation, and determination are executed. As described above, the control device 13 repeatedly transmits a control signal (a stop signal to the inspection position) to the robot 1 until the deviation falls within the range of the reference value. If it is determined that the deviation is within the range of the reference value, the control device 13 ends the position adjustment of the robot 1 (end effector 2).

  As described above, according to the present embodiment, the deviation between the command position of the end effector 2 and the realized position is calculated by the position accuracy calculation unit 23a of the control device 13, and the deviation is determined by the determination unit 23b. The position adjustment of the end effector 2 can be suitably executed. That is, the control device 13 completes the position adjustment when the deviation between the command position and the actual position is within a predetermined reference value range, but when the deviation is outside the reference value range. Continues to send a stop command to the robot 1 in order to continue this position adjustment. Thereby, the position adjustment can be reliably executed using the relative position accuracy without considering the absolute position accuracy of the end effector 2.

  In addition, when the determination by the determination unit 23b is performed, the reference value is set to a numerical value that is higher than the repeat position accuracy of the robot 1, so that the robot 1 can be used in the best state and the performance of the robot 1 is maximized. It can be used as much as possible.

  As described above, by manufacturing a product while using the position control system 11 according to the present embodiment, it becomes possible to reduce cycle time, shorten processes, and control the investment amount. Can be reduced.

  In addition, this invention is not limited to the structure of the said embodiment. Further, the present invention is not limited to the above-described effects. The present invention can be variously modified without departing from the gist of the present invention.

  In the above-described embodiment, the example in which the image 14 by the diffused laser light is projected from the projection device 15 is shown, but the present invention is not limited to this. For example, in the case where the positional displacement of the end effector 2 does not occur on one coordinate axis (for example, the x axis in the above-described embodiment) related to the orthogonal coordinate system or the positional displacement can be ignored, In addition, it is possible to project an image with laser light having high directivity.

  In the above embodiment, the projection device 15 has the cross-shaped slit 18 as an example. However, the present invention is not limited to this. For example, the projection device 15 can project (project) the shadow as an image 14 onto the screen 16 by irradiating the cross-shaped shielding member with light. In this case, the light source is not necessarily fixed to the tip of the robot 1 or the end effector 2, and the shielding member may be irradiated with diffused laser light from a position away from the robot 1.

DESCRIPTION OF SYMBOLS 1 Robot 2 End effector 11 Position control system 12 Measuring apparatus 13 Control apparatus 23a Position accuracy calculation part 23b Determination part

Claims (1)

In a position control system for performing position control of a robot having an end effector,
A measuring device for measuring the stop position of the end effector, and a control device for controlling the measuring device and the robot,
The control device is configured to transmit a stop command to instruct the robot to stop the end effector,
The control device includes a position accuracy calculation unit that calculates a deviation between a command position related to the stop command and a realization position of the end effector measured by the measurement device, and the deviation falls within a predetermined reference value range. A determination unit for determining whether or not there is,
The control device is configured to repeatedly transmit the stop command to the robot until the determination unit determines that the deviation is within a predetermined reference value range. .

Images